基于LBM的贯流式水轮机甩负荷特性研究

Study on load rejection characteristics of tubular turbine based on LBM

基于格子Boltzmann方法(LBM),采用壁面自适应局部涡黏模型,对原型贯流式水轮机甩额定负荷的瞬态过程进行了大涡模拟,获得了在活动导叶两段关闭方式下水轮机甩负荷过程中转轮转速、水力矩、轴向力等工作参数的变化规律,探讨了贯流式水轮机在甩负荷过程中导叶和转轮前后的水压变化.计算得到甩负荷过程中转轮最大转速上升率为36.7%,满足电站甩负荷调节的要求.较慢的导叶关闭速率可以降低水压力波动的幅度.对甩负荷过程中水轮机各过流部件内的瞬态流场进行了分析,结果表明:在水轮机甩负荷过程中,水流冲角的变化使得叶片表面产生低压区从而引起空化空蚀,在转轮和尾水管内部存在湍流涡及复杂的二次流动,影响系统的运行稳定性.

Based on the lattice Boltzmann method(LBM)and the wall adaptive local eddy viscous model,the large eddy simulation of the transient load rejection process of a prototype tubular turbine was carried out.The variation rules of the working parameters such as the rotational speed,the hydraulic moment and the axial force of the turbine during load rejection under the two-stage closure of the guide vanes were obtained,and the hydraulic pressure changes before and after guide vanes and runners were also analyzed and discussed.The maximum speed rise rate of runner is 36.7%during load rejection,meeting the requirement of load rejection regulation in power plant.Furthermore,it is found that the lower closure rate of the guide vanes can reduce the amplitude of water pressure fluctuation.The transient flow fields in all flow components of the turbine during load rejection were analyzed.Results show that the low pressure area on the blade surface is generated due to the change of water flow angle,causing cavitation erosion.Turbulent vortices and complex secondary flow exist in the runner and draft,affecting the operation stability of the system.